自己整LED問題

W = Watt = unit of power = (current)^2 x (resistance of the resistor).

e.g. if the current of the LED is 20mA (=0.02A) and the resistance of the resistor that connected in series with the LED is 100 ohm. The power dissipated in resistor is (0.02)^2 x 100 = 0.04 W.

原帖由 ryancmlam 於 2007-5-16 23:56 發表
W = Watt = unit of power = (current)^2 x (resistance of the resistor).

e.g. if the current of the LED is 20mA (=0.02A) and the resistance of the resistor that connected in series with the LED is ...

THX , 咁係咪所有LED行20mA架呢?

原帖由 magic-vtec 於 2007-5-16 17:38 發表

查實咁樣堅冇咁好......我試過咁樣燒.....每粒加會好d....
當然.....only電箱加1粒方便好多

p.s. 我問過好幾個人....佢地都話其實電阻落 ＋ / － 都ok架

冇分正負

原帖由 herbert1 於 2007-5-17 00:01 發表



THX , 咁係咪所有LED行20mA架呢?

It depends on the color of the LED. When you calculate the resistance, you need to know two parameters viz. "forward voltage drop"(Vf) and "norminal current"(In) of the LED. Different color have different value of (Vf) and (In). Siimply, if the supply voltage is V, the resistance of the resistor that needs to be connected in series with the LED is R = (V-Vf)/In.
e.g. If supply voltage = 6V, forward voltage = 3V and In= 20mA, R = (6-3)/0.02 = 150 ohm,

原帖由 ryancmlam 於 2007-5-17 07:14 發表


It depends on the color of the LED. When you calculate the resistance, you need to know two parameters viz. "forward voltage drop"(Vf) and "norminal current"(In) of the LED. ...

之但係買粒LED返黎都唔知Vf 同In係幾多??

原帖由 阿蛇 於 2007-5-16 18:08 發表



佢個用途我唔係太明白 如果想整6粒LED 咁係咪用承受1.5w既電阻

你可以 o甘講 o既
但你接唔接受到 o甘大粒電阻裝 o係架車上面先?
大 1W 的電阻, size 大幾倍的

原帖由 herbert1 於 2007-5-17 11:37 發表



之但係買粒LED返黎都唔知Vf 同In係幾多??

約數啦 ~ 你估依家做緊精密而敏感的線路咩 ....
俾 o野你睇 ...
http://forum.esmchina.com/FORUM_POST_1200205053_0.HTM

原帖由 觀星是答案 於 2007-5-17 11:51 發表

約數啦 ~ 你估依家做緊精密而敏感的線路咩 ....
俾 o野你睇 ...
http://forum.esmchina.com/FORUM_POST_1200205053_0.HTM

Wow............呢個網講得好詳細 , THX

琴日整左差唔多4個鐘.........雖然大部份燈都著......但係有2粒超光紅唔著.......4粒黃色超暗...............
計劃失敗......聽日都係羅比人整算喇...........